EP1069712B1 - Amplificateur optique à large bande - Google Patents

Amplificateur optique à large bande Download PDF

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Publication number
EP1069712B1
EP1069712B1 EP00401982A EP00401982A EP1069712B1 EP 1069712 B1 EP1069712 B1 EP 1069712B1 EP 00401982 A EP00401982 A EP 00401982A EP 00401982 A EP00401982 A EP 00401982A EP 1069712 B1 EP1069712 B1 EP 1069712B1
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signal
wavelength
type
optical
amplifier
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EP1069712A2 (fr
EP1069712A3 (fr
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Hiroji c/o Nippon Telegraph & Tel. Corp. Masuda
Junichi c/o Nippon Telegraph & Tel. Corp. Kani
Noboru c/o Nippon Telegraph & Tel. Corp Takachio
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Nippon Telegraph and Telephone Corp
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Nippon Telegraph and Telephone Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/293—Signal power control
    • H04B10/294—Signal power control in a multiwavelength system, e.g. gain equalisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2210/00—Indexing scheme relating to optical transmission systems
    • H04B2210/25—Distortion or dispersion compensation
    • H04B2210/258—Distortion or dispersion compensation treating each wavelength or wavelength band separately

Definitions

  • the present invention relates to an optical amplifier for use in optical fiber communication systems and optical signal processing systems.
  • FIG. 22 The basic configuration of a conventional optical amplifier is shown in Figure 22 .
  • This optical amplifier is comprised by two amplifying sections having different gain band regions (L-amplifying section and S-amplifying section), a divider, and a combiner, and attempts to broaden the operational bandwidths by coupling the two gain band regions in the wavelength domain.
  • L-amplifying section and S-amplifying section two amplifying sections having different gain band regions
  • a divider divider
  • a combiner attempts to broaden the operational bandwidths by coupling the two gain band regions in the wavelength domain.
  • dividers and combiners are utilized in constructing such optical amplifiers, and they can be classified as a dielectric multi-layer filter or a combination of fiber grating in association with circulator. Those based on dielectric multi-layer filter are reported in the following references.
  • wavelength division properties of these devices are not perfect, and problems are encountered depending on the manner and conditions of applying the amplifiers.
  • Figures 1A and 1B show the configuration of a conventional optical amplifier, where Figure 1A shows a design based on dielectric multi-layer filters of the long wavelength transmission type (L-type) for the divider and combiner, represented by L-divider (3) and L-combiner (4), and Figure 1B shows a design based on dielectric multi-layer filters of the short wavelength transmission type (S-type) for the divider and combiner, represented by S-divider (5) and S-combiner (6).
  • L-type long wavelength transmission type
  • S-type short wavelength transmission type
  • the amplifying section has a gain medium and a pumping section for excitation, and examples of such optical amplifiers are rare-earth doped fiber amplifier, fiber Raman amplifier and semiconductor laser amplifier.
  • the rare-earth doped fiber amplifiers include erbium-doped fiber amplifier and the like, and according to " Wideband erbium-doped fibre amplifiers with three-stage amplification", H. Masuda et. al., IEE Electronics Letters, vol. 34, no. 6, 1998, pp567-568 (Reference 8), it is advantageous when such an amplifier has a gain equalizer to broaden the region of flat gain because such an amplifier can produce a large total gam bandwidth.
  • optical amplifiers are generally designed to receive wavelength-multiplexed light signals, and in optical signal processing systems for instruments and the like, optical amplifiers are generally designed to receive wavelength- multiplexed light signals or single wavelength light signals.
  • Figures 2A and 2B show configurations of the divider, where Figure 2A represents an L-type dielectric multi-layer filter (L-divider), and Figure 2B represents an S-type dielectric multi-layer filter (S-divider).
  • the L-divider receives input light containing a short-wavelength ⁇ s and a long wavelength ⁇ l in the common port (c), and transmits a long wavelength ⁇ l from the transmission port ( l ) and reflects a short wavelength ⁇ s from the reflection port (s).
  • the S-divider receives input light containing a short-wavelength ⁇ s and a long wavelength ⁇ l in the common port (c), and reflects a long wavelength light ⁇ l from the reflection port ( l ) and transmits a short wavelength light ⁇ s from the transmission port (s).
  • Figures 3A and 3B show configurations of the combiner, where Figure 3A represents an L-type dielectric multi-layer filter (L-combiner), and Figure 3B represents an S-type dielectric multi-layer filter (S-combiner).
  • the L-combiner receives input light containing a short-wavelength ⁇ s from the reflection port (s) and a long wavelength ⁇ l from the transmission port ( l ), and outputs light containing a long wavelength ⁇ l and a short wavelength ⁇ s from the common port (c).
  • the S-combiner receives input light containing a short-wavelength ⁇ s from the transmission port (s) and a long wavelength ⁇ l from the reflection port ( l ), and outputs light containing a long wavelength ⁇ l and a short wavelength ⁇ s from the common port (c).
  • the dividers (L- and S-dividers) 3,.5 perform the steps described above, and divide the multiplexed signal light containing a long wavelength ⁇ l and a short wavelength ⁇ s into a long wavelength signal light ⁇ l and a short wavelength signal light ⁇ s, which are input into the respective amplifying sections (L-a and S-amplifying sections) 1, 2, and are combined in the combiners 4, 6 and multiplexed light signals are thus output.
  • Figures 4A and 4B show gain spectra obtained in the amplifying sections (L-, S-amplifying sections) 1, 2, where Figure 4A shows an overall view of the gain region while Figure 4B shows details of gains in the vicinities of the wave boundaries (wavelengths ⁇ tr-s to ⁇ tr- l ) of the L- and S-amplifying sections.
  • wavelengths in the L-amplifying section are denoted by ⁇ l * and those in the S-amplifying section are denoted by ⁇ s*
  • the peak gains in the L-, S-amplifying sections are denoted by G while the wavelength-specific gains for ⁇ l * , ⁇ s* are denoted by G*.
  • Figures 5A and 5B show loss spectra in the L-divider, and show the losses relating to a transmission loss between ports c and s, and the same between ports c and l (refer to Figures 2A and 2B ), which are denoted respectively by Lcs1 and Lc l 1 where 1 indicates that the losses are related to long wavelengths.
  • Figure 5A shows the loss in the overall view of the gain region and
  • Figure 5B shows the details of the loss in the wave boundary.
  • the loss becomes larger as the wavelength of the signal waves moves away from the respective boundary wavelengths (wavelengths ⁇ tr-s to ⁇ tr- l ) into fringes of the respective gain regions.
  • the loss Lcs1 between the port s (for reflected light) and the common port c is limited to a certain constant value, because of the contribution from residual reflection components in the dielectric multi-layer filter.
  • the difference in the wavelengths ⁇ tr-s to ⁇ tr- l (referred to as the boundary bandwidth) is typically 5 ⁇ 10 nm at a 15 ⁇ m wavelength, and the limiting value and the loss at the wavelength ⁇ s* are typically about 10 dB and 20 dB, respectively.
  • the boundary bandwidth and the slope of the curve of loss spectrum in the vicinity of the wave boundary are dependent on the parameters (composition and the number of layers of lamination) of the dielectric multi-layer filter.
  • Figures 6A and 6B show the loss spectra of the S-type divider, where Figure 6A, 6B relate, respectively, to the transmission losses between ports s and l , and between ports c and l shown in Figures 2A and 2B (referred to as Lcs2, Lcl2, where 2 indicates that the losses are related to short wavelengths).
  • Figure 6A refers to the overall view of the loss region and Figure 6B shows details of losses in the wave boundary.
  • Both Lcs2, Lcl2 show a tendency to increase as the wavelengths of the signal waves move away from the respective boundary wavelengths (wavelengths ⁇ tr-s to ⁇ tr- l ) into fringes of the gain regions.
  • the loss Lcs2 between the port l (for reflected light) and the common port c is limited to a certain constant value, which is caused by the contribution from residual reflection components in the dielectric multi-layer filter.
  • the difference in the wavelengths ⁇ tr-s to ⁇ tr- l (referred to as the boundary bandwidth) is typically 5 ⁇ 10 nm at a 15 ⁇ m wavelength, and the limiting value and the loss at the wavelength ⁇ s* are typically about 10 dB and 20 dB, respectively.
  • the boundary bandwidth and the slope of the curve of loss spectrum in the vicinity of the wave boundary are dependent on the parameters (composition and the number of layers of lamination) of the dielectric multi-layer filter.
  • the loss spectra of the L- and S-type combiners are the same as the loss spectra of the L- and S-type dividers shown in Figures 5 and 6 , because of the reciprocality of light propagation. That is, if the transmission ports are the same, the loss values are the same.
  • Figures 7A and 7B show loss spectra in the optical circuits of a conventional optical amplifier. The losses are incurred in the L- and S-amplifying sections, and the circuit loss is represented by a sum of the losses in the dividers and combiners, and are expressed in the units of dB.
  • Figure 7A shows the losses in the L-type divider and combiner shown in Figure 1A
  • Figure 7B shows the losses in the S-type divider and combiner shown in Figure 1B .
  • the loss value (denoted by U) in the S-amplifying section at a wavelength ⁇ l * is limited to 20 dB, which is twice the limit value (about 10 dB).
  • 20 dB and 10 dB correspond to non-dimensional numbers, 100 and 10, respectively, so that the former is ten times the latter.
  • the loss value (denoted by Ls) in the L-amplifying section at a wavelength ⁇ s* is limited to 20 dB, which is twice the limit value (about 10 dB). In other words, the loss of signal light at the wavelength ⁇ s* is limited to ten times the limit value.
  • the output light for example wavelength ⁇ l *, from its primary circuit (through the L-amplifying section) is affected by the contribution from the residual light in the reflection circuit (through the S-amplifying section).
  • the optical powers of the primary output light and the residual light are designated, respectively, by P and P*. If the value of P* is not sufficiently small compared with P, coherent interference is generated and interference noise will be superimposed on the signal light to cause operational problems. For example, in an optical communication system, an increase in bit error rate will lead to degradation of the system performance.
  • P and P* are related to the input power Pin (in units of dBm) according to the following expressions.
  • P - P * G - G * + L ⁇ l
  • G* is the gain in the residual circuit and U represents the circuit loss described in Figures 7A and 7B , and wavelength-dependent losses in the dividers and combiners are neglected for simplicity. If it is assumed that the difference between G and G* is smaller than U and can be neglected, the difference between P and P* is equal to L 1 from equation (2).
  • Ll is about 20 dB, but this value is not sufficiently large, so that interference noise is generated.
  • P and P* are related to the input power Pin (in units of dBm) according to the following expressions.
  • P - P * G - G * + Ls
  • Ls represents the circuit loss described in Figures 7A and 7B . If it is assumed, for simplicity, that the difference between G and G* is smaller than Ls and can be neglected, the difference between P and P* is equal to Ls from equation (4). In the example given in Figures 7A and 7B , Ls is about 20 dB, but this value is not sufficiently large, so that interference noise is generated.
  • the signal wavelength in the long wavelength region to produce a gain difference G-G* of les than 10 dB is designated by ⁇ l ** as indicated in Figures 4A and 4B , and the gain value at this wavelength is designated by G**.
  • the optical power difference P-P* is less than 30 dB.
  • FR-A-2 764 452 discloses a system having a multiple wavelength amplifier and a demultiplexer separating out the different optical wavelengths. Filtering separates the wavelengths out, and each wavelength set has an amplifier which individually adjusts the level of the wavelength signal. The signals are then recombined by a multiple coupler.
  • EP-A-0 841 764 discloses an optical amplifier according to the statement of claim 1.
  • the invention relates to an optical amplifier according to claim 1.
  • the invention also relates to an optical amplifier according to claim 6.
  • an optical amplifier comprising: an optical divider for dividing input signal light according to wavelengths; two amplifying sections disposed in parallel and having different wavelength amplification regions for amplifying respective light signals emitted from the optical divider; an optical combiner for combining the light signals output from the respective amplifying sections; and an optical filter disposed in series with at least one of the two amplifying sections for generating a loss in a specific wavelength region.
  • the optical amplifier of such a design enables to narrow the latent noise region by the action of the filter in generating a loss in residual reflection components created by the wave division effect in the optical divider so as to increase the gain performance of the signal processing circuit associated with the optical filter.
  • the object has also been achieved in another design of the optical amplifier comprising: an optical divider using a dielectric multi-layer filter for dividing input signal light according to wavelengths; two amplifying sections disposed in parallel and having different wavelength amplification regions for amplifying respective light signals emitted from the optical divider; and an optical combiner for combining light signals output from respective amplifying sections using a filter having a blocking wavelength region different than the dielectric multi-layer filter provided in the optical divider.
  • the optical amplifier of such a design enable to narrow the latent noise region as a result of improved gain in the signal processing circuits because the transmission region of the dielectric multi-layer filter used in the optical divider is different than the dielectric multi-layer filter used in the optical combiner.
  • the present optical amplifier provides benefits that the wavelength bandwidth of the latent noise region has been narrowed and, consequently, the bandwidth of useable wavelengths of signal light that can be used for optical processing purposes has been broadened.
  • Figure 8A shows a configuration based on an L-type divider and an S-type combiner (referred to as L-divider and S-combiner hereinafter), and Figure 8B shows a configuration based on an S-divider and an L-combiner.
  • Figure 9 shows the circuit loss spectra of the amplifier in the first configuration, relating the circuit losses through the L- and S-amplifying sections, representing a sum of the losses in the divider and combiner in units of decibels (dB).
  • This loss spectra are obtained from the loss spectra shown in Figures 5 and 6 which were explained in the section on the related art.
  • the loss values are typical values as described in the section concerned with the related art.
  • the wavelength region that shows less than 30 dB power difference, P-P*, in Figure 9 occurs from the vicinity of ⁇ s* to the vicinity of ⁇ l *.
  • This difference in the wavelengths (difference between the wavelengths in the vicinities of ⁇ s* and ⁇ l *) is considerably smaller than the difference in the corresponding wavelengths (difference between the wavelengths in the vicinities of ⁇ s** and ⁇ l **) described in the section concerned with the related art. That is, according to the first configuration, bandwidth of the signal waves affected by the interference noise is narrower compared with that of conventional amplifiers, because the residual reflection components have been reduced, thus enabling to expand the useable bandwidth of signal waves.
  • Figure 10A shows a configuration based on an L-divider and an L-combiner
  • Figure 10B shows a configuration based on an S-divider and an S-combiner.
  • the optical filter 7 in Figure 10A is a short wavelength transmission type and the optical filter 8 in Figure 10B is a long wavelength transmission type.
  • the filters 7, 8 include 2-port optical filters having dielectric multi-layer filters or fiber gratings that reflect those signal waves having wavelengths in the vicinities of boundary wavelengths.
  • optical amplifiers based on such filters 7 and 8 utilizing 2-port optical filter are made of dielectric multi-layer filters, amplifiers can be produced at lower cost compared with amplifiers based on other types of optical filters, because of the low cost of making dielectric multi-layer filters.
  • the filters 7 and 8 are made of fiber gratings, optical amplifiers utilizing such filters are advantageous because the insertion losses due to insertion of signal waves are smaller compared with the insertion losses experienced by other types of filters so that higher gain and output power as well as lower interference noise can be obtained from such optical amplifiers.
  • the optical filters 7, 8 are placed in the aft-stage of the L- and S-amplifying sections, they may be placed in series in the fore-stage.
  • the aft-stage placement is more advantageous than the fore-stage placement, because the interference noise is lower in such an arrangement.
  • Figure 11 shows a circuit loss spectrum of the optical amplifier based on the second configuration, especially the use of an L-divider and an L-combiner, shown in Figure 10A .
  • the optical filter 7 in this case is based on a 2-port optical filter having dielectric multi-layer filters, relating the circuit losses through the L- and S-amplifying sections, and representing a sum of the losses in the divider and combiner in units of decibels (dB).
  • dB decibels
  • the wavelength region that shows less than 30 dB power difference, P-P*, in Figure 11 occurs from the vicinity of ⁇ s** to the vicinity of ⁇ tr- l .
  • This difference in the wavelengths (difference between the wavelengths in the vicinities of ⁇ s** and ⁇ tr- l ) is considerably small than the difference in the corresponding wavelengths described in the section concerned with the related art. That is, according to the second configuration, bandwidth of the signal waves affected by the interference noise is narrower compared with that of conventional amplifiers, thus enabling to expand the bandwidth of useable signal wavelengths.
  • Figure 23 shows a third configuration of the optical amplifier.
  • the divider (1:1 division) and combiner are either fiber couplers (combiners), whose performance properties do not vary with wavelengths, or a combination of a fiber coupler and either a divider or a combiner made of dielectric multi-layer filters.
  • the signal wavelength ⁇ s in the short wavelength band is close to the wavelengths in the wave boundary between the long and short wavelength bands, such signal waves tend to mix with the long wavelengths in the long wavelength L-amplifying section, and therefore, such mixed wave components are eliminated by placing an optical filter in the aft-stage of the L-amplifying section.
  • the loss value in the optical filter for the mixed waves should be higher than 30 dB for the same reasons as explained earlier.
  • the fiber grating clearly serves a different purpose than the optical filter provided in the present invention as a constituting element for the purpose of eliminating residual reflection components.
  • Figure 12 shows an optical amplifier in Embodiment 1. This is an example of using an erbium doped fiber amplifier (EDFA) in the amplifying section.
  • EDFA erbium doped fiber amplifier
  • a regular EDFA for short wavelength band (S-type EDFA) 11 is used for processing short wavelength signals
  • a long wavelength band (L-type EDFA) 12 having the bandwidth enlarged by a gain equalizer, described in the section concerned with the related art, was used for processing long wavelength signals.
  • Figures 13A and 13B show schematic diagrams of the gain spectra of the amplifying sections (S-type EDFA and L-type EDFA) in Embodiment 1, where Figure 13A relates to the overall view of the spectrum and Figure 13B relates to the details of the spectrum near the wave boundary.
  • the wave boundary extends from 1562 to 1566 nm.
  • the number of layers of the dielectric multi-layer filter is approximately 100.
  • the peak gain of the amplifying section is 20 dB, and the gains for S-type EDFA and L-type EDFA at 1570 nm are 10 dB for each.
  • Figure 14 shows the circuit loss spectrum of the amplifier in Embodiment 1.
  • the boundary bandwidth in which the differential power P-P* of the signal waves is less than 30 dB is approximately 1560 ⁇ 1568 nm according to the results shown in Figures 13 , 14 . It means that the bandwidth of the "latent noise region" is 8 nm. On the other hand, in the conventional optical amplifiers based on L-type divider and S-type combiner, the corresponding boundary bandwidth is approximately 1561 ⁇ 1574, resulting in the bandwidth of the latent noise region of 13 nm.
  • the bandwidth of the latent noise region (wavelength region that cannot be used for signal waves because of interference noise effects) in the present optical amplifier is about a half of the conventional width (8/13 to be exact).
  • Figure 15 shows a configuration of the optical amplifier in Embodiment 2.
  • SLA semiconductor laser amplifier
  • the wavelength gain region of SLA can be changed by varying the semiconductor composition ratio.
  • short wavelength band SLA (S-type SLA) 13 and long wavelength band SLA (L-type SLA) 14 are being used, and they have primarily different composition ratios of semiconductors.
  • Figures 16A and 16B show schematic diagrams of the gain spectra of the amplifying sections (S-type and L-type SLA) in this embodiment, where Figure 16A relates to the overall spectrum and Figure 16B relates to the spectrum near the wave boundary.
  • the wave boundary extends from 1560 to 1570 nm.
  • the number of layers of the dielectric multi-layer filter is approximately 50.
  • the peak gain of the amplifying section is 20 dB, and the gains for S-type SLA 13 and L-type SLA 14 at 1585 nm are 10 dB for each.
  • Figure 17 shows the circuit loss spectrum of the amplifier in this embodiment.
  • the boundary bandwidth in which the differential power P-P* of the signal waves is less than 30 dB is approximately 1554 ⁇ 1576 nm according to the results shown in Figures 16 , 17 . It means that the width of the latent noise region is 22 nm. On the other hand, in the conventional optical amplifiers based on L-divider and S-combiner, the corresponding boundary bandwidth is approximately 1557 ⁇ 1595, resulting in the width of the latent noise region of 38 nm.
  • the width of the latent noise region (wavelength region that cannot be used for signal waves because of interference noise effects) in the present optical amplifier is about a half of the conventional width (22/38 to be exact).
  • Figure 18 shows a configuration of the optical amplifier in Embodiment 3.
  • SLA semiconductor laser amplifier
  • the wavelength gain region of SLA can be changed by varying the semiconductor composition ratio.
  • short wavelength band SLA (S-type SLA) 13 and long wavelength band SLA (L-type SLA) 14 are being used, they are primarily different in the semiconductor composition ratios.
  • the structure of the amplifying section in this embodiment is the same as that in Figures 16A and 16B .
  • the number of layers in the dielectric multi-layer filter, L-divider, L-combiner and the optical filter 15 used in the amplifier shown in Figure 18 is approximately 50.
  • Figure 19 shows circuit loss spectrum for the amplifier in this embodiment.
  • the boundary bandwidth in which the differential power P-P* of the signal waves is less than 30 dB is approximately 1556 ⁇ 1570 nm according to the results shown in Figures 16 , 19 . It means that the bandwidth of the latent noise region is 14 nm. On the other hand, in the conventional optical amplifiers based on L-divider and L-combiner, the corresponding boundary bandwidth is approximately 1557 ⁇ 1595, giving the width of the latent noise region as 38 nm.
  • the width of the latent noise region (wavelength region that cannot be used for signal waves because of interference noise effects) in the present optical amplifier is about a third of the conventional width (14/38 to be exact).
  • Figure 20 shows a configuration of the optical amplifier in Embodiment 4. This is an example of using a fiber Raman amplifier (FRA) in the amplifying section.
  • FRA fiber Raman amplifier
  • the wavelength gain region of FRA can be changed by varying the pumping wavelength.
  • the amplifier in this embodiment is a 3-wavelength band amplifier, based on the concept outlined earlier to regard an amplifier for two wavelength bands as one amplifying section.
  • a short wavelength band FRA (S-type FRA) 16 and a long wavelength band FRA (L-type FRA) 17 are used to construct a 2-wavelength band optical amplifier, which is designated as the new long wavelength band FRA (L*-type FRA), and a short wavelength band FRA (S*-type FRA) 18 is used at the short wavelength end of the new L*-type FRA, as a third amplifying section, in association with an L-divider (3') and an S-combiner (6').
  • the outlines of the gain spectra of the amplifying sections are shown in Figure 21 .
  • the number of layers of the dielectric multi-layer filters used in the L-divider and S-combiner used in this embodiment is approximately 50. Similar to Embodiment 3, the width of the latent noise region relates, in this case, to the widths of the two wave boundaries in the 3-wavelength bands, and both are 14 nm. On the other hand, in the conventional optical amplifier, the corresponding boundary bandwidth is 38 nm.
  • the width of the latent noise region (wavelength region that cannot be used for signal waves because of interference noise effects) in the present optical amplifier is about a third of the conventional width (14/38 to be exact).
  • Figure 24 shows a configuration of the optical amplifier in Embodiment 5.
  • the amplifying section is comprised by an S-type EDFA for short wavelengths, an L-type EDFA for long wavelengths, and the divider and combiner are made of fiber couplers that are not dependent on wavelength and having a 1:1 split ratio.
  • a fiber grating is placed in each aft-stages of the S-EDFA and L-EDFA for eliminating long wavelength signal waves and short wavelength signal waves, respectively, to serve as optical filters, and are respectively referred to as L-fiber-grating and S-fiber-grating.
  • the S- and L-EDFA respectively amplify signal waves having wavelengths in a range of 1530 ⁇ 1560 nm and wavelengths in a range of 1570 ⁇ 1600 nm.
  • the S-fiber-grating filters only those signal waves having wavelengths in a range of 1550 ⁇ 1560 nm to generate a loss value of more than 20 dB.
  • the L-EDFA generates a gain of more than 20 dB for wavelengths of signal waves in a range of 1570 ⁇ 1600 nm, at the same time, a gain of less than 10 dB for wavelengths of signal waves in a range of 1550 ⁇ 1560 nm, and a loss of more than 10 dB for wavelengths of signal waves in a range of 1530 ⁇ 1550 nm.
  • the L-fiber-grating filters only those waves having wavelengths in a range of 1570 ⁇ 1600 nm to generate a loss value of more than 20 dB.
  • the S-EDFA generates a gain of more than 20 dB for wavelengths of signal waves in a range of 1530 ⁇ 1560 nm, at the same time, a gain of less than 10 dB for wavelengths of signal waves in a range of 1570 ⁇ 1600 nm.
  • Fiber gratings having such optical properties can be produced readily at low cost.
  • non-useable wavelength range for signal waves is 10 nm that exists between 1560 ⁇ 1570 nm. This value is less than half the value generally observed in the conventional technologies and is clearly less than the conventional amplifiers that do not use L- and S-fiber-gratings.
  • the divider and combiner used in the input section and output section of the amplifier have a split ratio of 1: 1 and no wavelength dependency, compared with an amplifier based on wave-separation type divider and combiner such as dielectric multi-layer filters, an excess loss value of nearly 3 dB is generated.
  • fiber couplers having a 1:1 split ratio and no wavelength dependency have an advantage that they generally cost less than other types of filters. Also, the excess loss can be compensated by providing additional means.
  • Figure 25 shows a configuration of the optical amplifier in Embodiment 6.
  • This configuration may appear similar to the one for Embodiment 1, but a significant difference is that the divider is based on a dielectric multi-layer filter and the combiner is based on a fiber coupler having a 1:1 split ratio and no wavelength dependency. Also, an S-fiber-grating is placed in the aft-stage of the L-EDFA as an optical filter for filtering signal waves in the short wavelength hand.
  • the S-fiber-grating filters only those signal waves having wavelengths in a range of 1550—1560 nm to generate a loss value of more than 10 dB.
  • the L-EDFA generates a gain of 20 dB for wavelengths of signal waves in a range of 1570—1600 nm, at the same time, a gain of less than 10 dB for wavelengths of signal waves in a range of 1550—1560 nm, and a loss of more than 10 dB for wavelengths of signal waves in a range of 1530—1550 nm.
  • the S-divider generates a loss of more than 10 dB for signal waves in a range of 1530— 1560 nm between input port (c) and port (l) connecting to the L-EDFA.
  • the latent noise bandwidth is 10 nm that exists between 1560—1570 nm. This value is clearly less than the conventional amplifiers that do not use S-fiber-gratings, and is less than half the value generally observed in the conventional technologies.

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Claims (7)

  1. Amplificateur optique comprenant :
    un diviseur optique de première longueur d'onde (3,5) utilisant un filtre multicouche diélectrique et ayant un port d'entrée de signal lumineux (c), un port de sortie d'émission et un port de sortie de réflexion, pour recevoir un signal lumineux contenant au moins une première longueur d'onde (λl) et une deuxième longueur d'onde (λs) à travers le port d'entrée pour produire en sortie un premier signal de la première longueur d'onde à travers le port de sortie d'émission en émettant le premier signal du signal lumineux et un deuxième signal de la deuxième longueur d'onde à travers le port de sortie de réflexion en réfléchissant le deuxième signal du signal lumineux ;
    une première section d'amplification (1) pour amplifier le premier signal ;
    une seconde section d'amplification (2) pour amplifier le deuxième signal ;
    caractérisé en ce que l'amplificateur optique comprend un combineur optique de deuxième longueur d'onde (6, 4) utilisant un filtre et ayant un port d'entrée de réflexion, un port d'entrée d'émission et un port de sortie commun (c), pour recevoir le premier signal amplifié à travers le port d'entrée de réflexion et le deuxième signal amplifié à travers le port d'entrée de transmission, et pour combiner le premier signal amplifié et le deuxième signal amplifié en réfléchissant le premier signal amplifié et en transmettant le deuxième signal amplifié afin de produire en sortie un signal lumineux combiné à travers le port de sortie commun.
  2. Amplificateur optique selon la revendication 1, dans lequel la première longueur d'onde est une longueur d'onde longue et la deuxième longueur d'onde est une longueur d'onde courte, et dans lequel le premier diviseur optique de longueur d'onde (3) est un filtre multicouche diélectrique de type à transmission en longueur d'onde longue et le second combineur optique de longueur d'onde (6) est un filtre multicouche diélectrique de type à transmission en longueur d'onde courte.
  3. Amplificateur optique selon la revendication 1, dans lequel la première longueur d'onde est une longueur d'onde courte et la deuxième longueur d'onde est une longueur d'onde longue, et dans lequel le premier diviseur optique de longueur d'onde (5) est un filtre multicouche diélectrique de type à transmission en longueur d'onde courte et le second combineur optique de longueur d'onde (4) est un filtre multicouche diélectrique de type à transmission en longueur d'onde longue.
  4. Amplificateur optique selon la revendication 2, dans lequel la première section d'amplification de signal est un amplificateur à fibre dopée à l'erbium (EDFA) de type bande de longueur d'onde longue (type L) (12), et la seconde section d'amplification de signal est un EDFA de type bande de longueur d'onde courte (type S) (11).
  5. Amplificateur optique selon la revendication 3, dans lequel la première section d'amplification de signal est un amplificateur laser à semiconducteurs (SLA) (14) du type à bande de longueur d'onde longue (type L) (14), et la seconde section d'amplification de signal est un SLA du type à bande de longueur d'onde courte (type S) (13).
  6. Amplificateur optique caractérisé en ce qu'il comprend :
    un premier diviseur optique du type à transmission en longueur d'onde longue (diviseur L 3'), ayant un port d'entrée de signal lumineux (c), un premier port de sortie (1), et un second port de sortie (s), pour recevoir un signal lumineux contenant une première longueur d'onde (λ1), une deuxième longueur d'onde (λs) et une troisième longueur d'onde (λs*) à travers le port d'entrée pour produire en sortie un premier signal de la première longueur d'onde et de la deuxième longueur d'onde à travers le premier port de sortie et un deuxième signal de la troisième longueur d'onde à travers le second port de sortie ;
    un amplificateur Raman à fibre du type à bande de longueur d'onde longue combiné (FRA de type L*) pour amplifier le premier signal ;
    un amplificateur Raman à fibre du type à bande de longueur d'onde courte (FRA de type s*) (18) pour amplifier le deuxième signal ; et
    un premier combineur optique du type à transmission en longueur d'onde courte (combineur S 6'), ayant un premier port d'entrée (1), un second port d'entrée (s) et un port de sortie commun (c), pour recevoir le premier signal amplifié à travers le premier port d'entrée et le deuxième signal amplifié à travers le second port d'entrée, et pour combiner le premier signal et le deuxième signal pour produire en sortie le signal lumineux à travers le port de sortie commun.
  7. Amplificateur optique selon la revendication 6 dans lequel le FRA de type L* comprend :
    un second diviseur optique du type à transmission en longueur d'onde longue (diviseur L 3), ayant un port d'entrée de premier signal (c), un premier port de sortie (1) et un second port de sortie (s), pour recevoir le premier signal contenant la première longueur d'onde (λ1) et la deuxième longueur d'onde (λs) à travers le port d'entrée de premier signal afin de produire en sortie un troisième signal de la première longueur d'onde à travers le premier port de sortie et un quatrième signal de la deuxième longueur d'onde à travers le second port de sortie ;
    un amplificateur Raman à fibre du type à bande de longueur d'onde longue (FRA de type L) (17) pour amplifier le troisième signal ;
    un amplificateur Raman à fibre du type à bande de longueur d'onde courte (FRA de type S) (16) pour amplifier le quatrième signal ; et
    un second combineur optique de type à transmission en longueur d'onde courte (6), ayant un premier port d'entrée (1), un second port d'entrée (s) et un port de sortie commun (c), pour recevoir le troisième signal amplifié à travers le premier port d'entrée et le quatrième signal amplifié à travers le second port d'entrée, et pour combiner le troisième signal et le quatrième signal pour produire en sortie le premier signal à travers le port de sortie commun.
EP00401982A 1999-07-12 2000-07-10 Amplificateur optique à large bande Expired - Lifetime EP1069712B1 (fr)

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US20020196530A1 (en) 2002-12-26
EP1069712A2 (fr) 2001-01-17
DE60040192D1 (de) 2008-10-23
US6583924B2 (en) 2003-06-24
US6469826B1 (en) 2002-10-22
EP1069712A3 (fr) 2002-01-09

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